What HP engine do I need for river cruising?

[Jaffa_Cake Keith]

Hi,

I’m looking at buying a boat with a 

BMC 1.5 diesel • 30hp at

3,000rpm  engine. Other NB’s seem to have 40 to 45 hp engines. Would 30 ho be enough power for river cruising or canals only?

If it could be used on rivers would that include tidal rivers? 
Thanks,

Keith

[LadyG]

What type of boat

What size of boat.

Which type of cruising do you plan?

Any boat can go anywhere, but they may not be suited. 

 

[booke23]

1hp was enough back in the day! 

 

16 minutes ago, LadyG said:

What type of boat

What size of boat.

Which type of cruising do you plan?

Any boat can go anywhere, but they may not be suited. 

 

^^^We need to know this. 

 

[Tony Brooks]

15 minutes ago, Jaffa_Cake Keith said:

Hi,

I’m looking at buying a boat with a 

BMC 1.5 diesel • 30hp at

3,000rpm  engine. Other NB’s seem to have 40 to 45 hp engines. Would 30 ho be enough power for river cruising or canals only?

If it could be used on rivers would that include tidal rivers? 
Thanks,

Keith

 

I had a Bukh DV36 in a 54ft narrowboat, so almost an identical BHP but possibly a tiny fraction more torque, and I had no problems on the Thames in high water on yellow boards and also the tidal Trent BUT:

 

I worked on the Thames on a hire fleet and had to move boats in floods.

I know how to read the water to use flow to assist safe navigation and boat handling.

I know when it is wise to tie up and when it is vital to tie up and sit the flood out.

 

So it is far more important to have a competent skipper than loads of power, in fact an incompetent could be a danger to themselves if they thought a powerful engine would keep them safe.

 

Look at the BHP of full length working boats, possibly 18 BHP or less, and they coped just fine.

 

[alan_fincher]

3000 RPM would of course been perfectly normal on a BMC B series engine in automotive use.

 

However I don't think 3,000 rpm would be a good idea for a similar engine set up for canal boat use.

 

When we had this engine I don't believe we ever got beyond 2,000 rpm even when thrashing it.  Normal cruising was usually in the range 1,200 to 1,400 RPM

Edited February 26 by alan_fincher

[nb Innisfree]

Innisfree (60' narrowboat) 1st engine was 33bhp, enough for rivers but if batteries were in bulk charge the 100amp 24v alternator took enough power to bring max rpm (theoretical 2k rpm) down to about 1750rpm from 1950rpm. 2nd engine was 40 bhp @ 3k rpm (reworked prop)  and had a few bhp spare at full alt output so was ok, we only ever used max rpm for emergency stops (narrow bridges & oncoming boats!) 

[Tonka]

19 minutes ago, Tony Brooks said:

 

I had a Bukh DV36 in a 54ft narrowboat, so almost an identical BHP but possibly a tiny fraction more torque, and I had no problems on the Thames in high water on yellow boards and also the tidal Trent BUT:

 

I worked on the Thames on a hire fleet and had to move boats in floods.

I know how to read the water to use flow to assist safe navigation and boat handling.

I know when it is wise to tie up and when it is vital to tie up and sit the flood out.

 

So it is far more important to have a competent skipper than loads of power, in fact an incompetent could be a danger to themselves if they thought a powerful engine would keep them safe.

 

Look at the BHP of full length working boats, possibly 18 BHP or less, and they coped just fine.

 

Had a 50ft Mike Heywood narrowboat on the Thames with a BMC 1.5. Been out on red boards on the Thames. Been across the Shepperton Weir whirlpool. 

I think the BMC 1.5 is higher hp rated then the current BD3 but I know which one looks better to me

[IanD]

23 minutes ago, Tony Brooks said:

 

I had a Bukh DV36 in a 54ft narrowboat, so almost an identical BHP but possibly a tiny fraction more torque, and I had no problems on the Thames in high water on yellow boards and also the tidal Trent BUT:

 

I worked on the Thames on a hire fleet and had to move boats in floods.

I know how to read the water to use flow to assist safe navigation and boat handling.

I know when it is wise to tie up and when it is vital to tie up and sit the flood out.

 

So it is far more important to have a competent skipper than loads of power, in fact an incompetent could be a danger to themselves if they thought a powerful engine would keep them safe.

 

Look at the BHP of full length working boats, possibly 18 BHP or less, and they coped just fine.

 

There's also the question for river use -- especially with older BMC engines which may have small skin tanks -- of whether the engine and cooling system can sustain full power for what could be several hours going upstream against a current -- and whether the steerer can bear the noise and vibration from an engine doing this... 😉 

 

The old working boats had low-speed engines which were quite happy to run flat-out all day, and without needing ear defenders.

 

The BUKH DV36 is also a heavy-duty engine designed for continuous use, and (if properly cooled) should have no problem being run flat-out -- might be a bit noisy though?

 

Who knows whether the BMC is set up to do this -- maybe it is, but many such boats weren't and don't like being run at high revs/loads for long periods without overheating. In which case the BMC "30hp" is not really comparable with the BUKH "30hp" or even the trad boat "18hp"... 😞 

[matty40s]

I've got a 18hp powering a 70ft narrowboat.

 

I've been in charge on the Thames, Trent and Severn(including tidal sections), Avon, Soar, Nene, Lee and Stort, Caldon, and the boat has also been on the Wey and t'other Avon down to Bristol. The Soar and Trent have both been done in Amber and Red in certain parts.

 

[magnetman]

A good BMC 1.5D with the right gearbox and prop is ideal. 

 

I knew a geyser who had a 64ft narrow with a BMC 1.5D. He got everywhere a 64ft can go. He even ran the central heating off it. 

 

The argument about tidal water and flowing rivers is firstly go with the tide not against it* and secondly don't navigate on rivers in red boards/strong stream as it is dangerous anyway. 

 

It'll be fine if propped right. 

 

* yes sometimes one needs to punch a bit of tide but thats not the same as doing several hours against a fast running tide. 

 

 

[Tony Brooks]

7 minutes ago, IanD said:

There's also the question for river use -- especially with older BMC engines which may have small skin tanks -- of whether the engine and cooling system can sustain full power for what could be several hours going upstream against a current -- and whether the steerer can bear the noise and vibration from an engine doing this... 😉 

 

The old working boats had low-speed engines which were quite happy to run flat-out all day, and without needing ear defenders.

 

The BUKH DV36 is also a heavy-duty engine designed for continuous use, and (if properly cooled) should have no problem being run flat-out -- might be a bit noisy though?

 

Who knows whether the BMC is set up to do this -- maybe it is, but many such boats weren't and don't like being run at high revs/loads for long periods without overheating. In which case the BMC "30hp" is not really comparable with the BUKH "30hp" or even the trad boat "18hp"... 😞 

 

The BMC 1.5 manual gives the maximum revs as 4500 RPM so 30BHP & 3000 rpm is 1/3 less than maximum revs. I know the continuous revs will be less than this, but with a boat the prop will almost certainly hold the revs down, as it does on the Bukh.

 

A Bukh would overheat with an undersized skin tank so that is a boat & installation issue, not one of BHP.

 

We put 1.5s in 35 ft wide beam GRP cruisers and did not have problems, even on red boards, but would not move them in known problem aeas like Windsor/Eton bridge or try to put them Maidenhead bridge when there was more than an inch or water drop through the arches.

[blackrose]

2 hours ago, IanD said:

There's also the question for river use -- especially with older BMC engines which may have small skin tanks -- of whether the engine and cooling system can sustain full power for what could be several hours going upstream against a current -- and whether the steerer can bear the noise and vibration from an engine doing this... 😉 

 

This is a good point. It doesn't matter how many hp you have or whether you have a well matched gearbox and prop if your cooling system can't manage. 

 

For the OP's reference, skin tank area should be based on about 1ft sq/4-5hp of engine power.

Edited February 26 by blackrose

[IanD]

1 hour ago, Tony Brooks said:

 

The BMC 1.5 manual gives the maximum revs as 4500 RPM so 30BHP & 3000 rpm is 1/3 less than maximum revs. I know the continuous revs will be less than this, but with a boat the prop will almost certainly hold the revs down, as it does on the Bukh.

 

A Bukh would overheat with an undersized skin tank so that is a boat & installation issue, not one of BHP.

 

We put 1.5s in 35 ft wide beam GRP cruisers and did not have problems, even on red boards, but would not move them in known problem aeas like Windsor/Eton bridge or try to put them Maidenhead bridge when there was more than an inch or water drop through the arches.

 

There's certainly no problem with the BMC given a good installation/skin tank, but from various postings (as well as bitter experience) that's just what many didn't have... 😞 

[Tonka]

21 minutes ago, IanD said:

 

There's certainly no problem with the BMC given a good installation/skin tank, but from various postings (as well as bitter experience) that's just what many didn't have... 😞 

How many HP would an electric motor for river use have to be ?

[IanD]

29 minutes ago, Tonka said:

How many HP would an electric motor for river use have to be ?

15kW/20hp is fine, so long as it'll sustain that for at least a couple of hours. Which a good installation will, obviously... 😉

[Tonka]

13 minutes ago, IanD said:

15kW/20hp is fine, so long as it'll sustain that for at least a couple of hours. Which a good installation will, obviously... 😉

So why wouldn't a 20hp combustion engine be enough for river use.

 

[IanD]

Just now, Tonka said:

So why wouldn't a 20hp combustion engine be enough for river use.

 

It is, if it's capable of running at 20hp continuously -- and without sounding like it's going to expire or deafen the steerer.

 

Just like the boats the ODGs used for years... 😉

[Tonka]

5 minutes ago, IanD said:

It is, if it's capable of running at 20hp continuously -- and without sounding like it's going to expire or deafen the steerer.

 

Just like the boats the ODGs used for years... 😉

Presumably the battery charging and gearbox takes some horsepower which is why they go for 30 HP plus so as after taking the losses out you still have 20 HP to the prop

[blackrose]

15 hours ago, booke23 said:

1hp was enough back in the day! 

 

 

Turning against a decent current on a river? Every time the engine size question comes up someone replies with the old 1hp cliché (even though they've probably got 30hp+ on their own boat). 1hp might be fine on a canal, but the OP specifically asked about river cruising.

Edited February 27 by blackrose

[Tonka]

16 minutes ago, blackrose said:

 

Turning against a decent current on a river? Every time the engine size question comes up someone replies with the old 1hp cliché (even though they've probably got 30hp+ on their own boat). 1hp might be fine on a canal, but the OP specifically asked about river cruising.

I don't think a horse is equal to 1 HP in an engine

[IanD]

12 hours ago, Tonka said:

Presumably the battery charging and gearbox takes some horsepower which is why they go for 30 HP plus so as after taking the losses out you still have 20 HP to the prop

Modern boats are generally overpowered if you just consider rated engine power, but you also need to consider what the steerer is willing to put up with. Pretty much all the boats with modern engines I've ever been on have got pretty unpleasant as far as noise and vibration is concerned well below maximum rpm, and are horrible flat out -- you certainly wouldn't want to stand over one doing this for a couple of hours.

 

So for a modern boat with a "40hp" engine, the *usable* power is maybe half this (at 80% of maximum rpm) -- which gets us back to 20hp...

[Tony Brooks]

17 minutes ago, blackrose said:

 

Turning against a decent current on a river? Every time the engine size question comes up someone replies with the old 1hp cliché (even though they've probably got 30hp+ on their own boat). 1hp might be fine on a canal, but the OP specifically asked about river cruising.

 

and that is where reading the water and knowing how to use it to your advantage come to the fore rather than any likely to be installed engien power.

[Jonny P]

20 minutes ago, Tonka said:

I don't think a horse is equal to 1 HP in an engine

1hp was originally estimated to be the continuous rating of a horse but in short bursts a horse can achieve something like 15hp.

 

Given that one horse could pull two fully laden canal boats for 18 hours a day every day and a modern leisure at boat at the same kind of speed is perhaps outputting 5hp it does seem that equating one horse to 1hp for canal work is an underestimate.

 

A lot of the anomalies we see in threads such as this come from the fact that we use the term power in a slightly different way to its true scientific meaning.

Edited February 27 by Jonny P

[magnetman]

Jaffa Cake Keith "I’m looking at buying a boat with a 

BMC 1.5 diesel" 

 

Without knowing anything else it is difficult to comment. 

 

It could be a 72ft x 13ft wide bean..

 

I think he wants to have his jaffa cake and eat it. 

[Tonka]

4 minutes ago, IanD said:

Modern boats are generally overpowered if you just consider rated engine power, but you also need to consider what the steerer is willing to put up with. Pretty much all the boats with modern engines I've ever been on have got pretty unpleasant as far as noise and vibration is concerned well below maximum rpm, and are horrible flat out -- you certainly wouldn't want to stand over one doing this for a couple of hours.

 

So for a modern boat with a "40hp" engine, the *usable* power is maybe half this (at 80% of maximum rpm) -- which gets us back to 20hp...

Isn't the rated horsepower of an engine over rated. I remember my father in law used to talk about true horsepower of an engine. He used to say that a 1500 cc engine had a true horsepower of 15 and a 3000 cc engine had a true horsepower of 30. Which when I think of my 3100 cc BD3 compared to our previous 1500 cc BMC makes a lot of sense, yet if you look at the rated horsepower the BMC is higher